<template>
  <div class="spec-preview">
    <img :src="defaultImg" />
    <div class="event" @mousemove="eventMouseMove"></div>
    <div class="big">
      <img :src="defaultImg" ref="bigImgEle" />
    </div>
    <div class="mask" ref="maskEle"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: ["skuImageList"],
  computed: {
    defaultImg() {
      return this.skuImageList.filter((item) => {
        return item.isDefault === "1";
      })[0]?.imgUrl;
    },
  },
  methods: {
    // 放大镜
    eventMouseMove(e) {
      // 获取鼠标到外层元素的距离
      const mouseToOut = {
        left: e.offsetX,
        top: e.offsetY,
      };

      // 计算 mask 的位置
      const maskLocation = {
        x: mouseToOut.left - this.$refs.maskEle.offsetWidth / 2,
        y: mouseToOut.top - this.$refs.maskEle.offsetHeight / 2,
      };

      // 临界值修正
      if (maskLocation.x < 0) {
        maskLocation.x = 0;
      } else if (
        maskLocation.x >
        e.target.clientWidth - this.$refs.maskEle.offsetWidth
      ) {
        maskLocation.x = e.target.clientWidth - this.$refs.maskEle.offsetWidth;
      }
      if (maskLocation.y < 0) {
        maskLocation.y = 0;
      } else if (
        maskLocation.y >
        e.target.clientWidth - this.$refs.maskEle.offsetHeight
      ) {
        maskLocation.y = e.target.clientWidth - this.$refs.maskEle.offsetHeight;
      }

      // 控制 mask 的位置
      this.$refs.maskEle.style.left = maskLocation.x + "px";
      this.$refs.maskEle.style.top = maskLocation.y + "px";

      // 控制 bigImg 的位置
      this.$refs.bigImgEle.style.left = -2 * maskLocation.x + "px";
      this.$refs.bigImgEle.style.top = -2 * maskLocation.y + "px";
    },
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
